JPH08276495A - Heat-shrinkable polystyrenic tube - Google Patents

Abstract

PURPOSE: To obtain a heat-shrinkable polystyrenic tube suitable for coating a dry battery can and good in coating processability. CONSTITUTION: A heat-shrinkable polystyrenic tube is obtained by stretching a tube composed of impact-resistant polystyrene having 3-15wt.% of conjugated diene hydrocarbon polymer particles dispersed therein and suitable for coating the zinc can of a dry battery. This tube has stiffness (rigidity), strength and inner surface slip properties suitable for the insertion of a dry battery in a dry battery automatic coating apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polystyrene tube which is mainly used for coating dry battery cans and which has excellent coating workability and provides a good shrink finish.

[0002]

2. Description of the Related Art As a heat-shrinkable tube for coating a zinc can of a dry battery (for interior), one made of polyvinyl chloride is well known. However, in recent years, a heat-shrinkable tube made of a raw material containing no halogen-based element has been demanded from the viewpoint of environmental problems such that hydrogen chloride is generated when polyvinyl chloride is incinerated. A styrene-butadiene block copolymer can be mentioned as one of the candidates for the raw material because it is put to practical use in the field of shrink film.

[0003]

However, since the tube obtained from this styrene-butadiene block copolymer is inferior in slippage on the inner surface, the opening of the tube and the insertability of the dry battery are poor, and a high-speed automatic coating device is provided. However, there is a problem in that it is difficult to coat with.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides an inexpensive heat-shrinkable polystyrene-based tube which solves the above-mentioned inconvenience, has a good inner surface slip property, and uses a general-purpose raw material. So, the main point is
It is a heat-shrinkable polystyrene-based tube obtained by stretching a tube made of impact-resistant polystyrene having 3 to 15% by weight of conjugated diene-based hydrocarbon polymer particles dispersed therein. In the tube of the present invention, by stretching, the conjugated diene hydrocarbon polymer particles in the impact-resistant polystyrene project to the surface, and in particular, the slipperiness of the inner surface of the tube can be greatly improved.

The present invention will be described in detail below. Impact-resistant polystyrene (hereinafter referred to as HI
(Sometimes abbreviated as PS) is a dispersion of conjugated diene hydrocarbon polymer particles in a styrene polymer. Examples of the styrene polymer include styrene,
Homopolymers such as o-methylstyrene, p-methylstyrene and α-methylstyrene, copolymers thereof, copolymers containing a copolymerizable monomer other than styrene hydrocarbon, and the like, and mixtures thereof. May be

Conjugated diene hydrocarbon polymer particles (hereinafter,
It may be abbreviated as rubber particles) as long as it exhibits rubber elasticity at room temperature, and examples thereof include homopolymers such as butadiene, isoprene, and 1,3-pentadiene, their copolymers, and conjugated diene hydrocarbons. There are copolymers containing other copolymerizable monomers (eg styrene) other than
It may be a thermoplastic elastomer. As a polymerization mode of HIPS, any of radical polymerization, anion polymerization and the like can be adopted.

In the above HIPS, the amount of rubber particles is H
It is important to be in the range of 3 to 15% by weight, based on the amount of IPS. If the amount of rubber particles exceeds 15% by weight, the tensile modulus in the length direction of the tube is 150 kgf /
It becomes smaller than mm ² , and the rigidity of the tube becomes low, making it unsuitable for a high-speed automatic coating device. On the other hand, if it is less than 3% by weight, the surface protrusion of rubber particles is reduced and the coefficient of kinetic friction on the inner surface of the tube is larger than 0.4, causing problems such as insertion of dry batteries in coating with an automatic coating machine for dry batteries, and drop impact. It is unsuitable because it breaks.

The average particle diameter of the rubber particles is 0.5-5.
μm is preferred. If the average particle size exceeds 5 μm, the tensile strength in the length direction becomes lower than 300 kgf / cm ² , and the tensile strength of the automatic coating apparatus with respect to tension is somewhat unsatisfactory, and the stretchability becomes poor. On the other hand, if it is less than 0.5 μm, the rubber particles are not sufficiently raised on the surface of the tube, the surface roughness required for inserting the dry battery in the automatic coating device cannot be exhibited, and the slipperiness is poor and the insertion trouble is likely to occur. Further, the effect of improving the drop impact property is also insufficient. The average particle diameter can be obtained by number-averaging from photographs taken by an ultrathin section method using a transmission electron microscope.

In order to use the tube of the present invention as an interior shrinkable tube for coating a zinc can of a dry battery, it is necessary that the inner surface of the tube has a dynamic friction coefficient of 0.4 or less, preferably 0.3 or less. Is. If the coefficient of kinetic friction of the inner surface of the tube is larger than 0.4, it is not suitable because the trouble of inserting the dry battery is likely to occur in the coating of the dry battery with the automatic coating machine.

The coefficient of dynamic friction of 0.4 or less can be achieved by appropriately selecting the amount and particle diameter of the rubber particles, the stretching temperature, etc., but if further improvement is desired, the lubricant of the composition should be added. Addition is preferred. Examples of organic lubricants include hydrocarbons such as paraffin, microwax, and low molecular weight polyethylene; fatty acids such as higher fatty acids and oxyfatty acids; fatty acid amides such as monofatty acid amides and alkylenebisfatty acid amides; fatty acid lower alcohol esters, Examples include ester systems such as fatty acid polyhydric alcohol esters; alcohol systems such as fatty alcohols, polyhydric alcohols, polyglycols and polyglycerols; metal soap systems.

Further, an inorganic lubricant which is an inert fine particle such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate and lithium fluoride may be contained. The addition amount is appropriately determined according to the degree of decrease in the dynamic friction coefficient.

The composition comprising the components described above can be mixed with a usual kneader, but it is preferable to use an extruder, particularly a twin-screw extruder, from the viewpoint of easy operation. Alternatively, it may be dry-blended and directly extruded.

The mixed composition is extruded into a tube by an extruder with an annular die. The unstretched tube is tubularly stretched in the length direction and the radial direction. At that time, the stretching ratio is 1 to 1.7 times in the length direction, preferably 1 to 1.4 times, and 1.7 to 4 times in the radial direction, preferably 1.8 to 3.5. Double. The stretching temperature is preferably as low as possible so long as the thickness unevenness is not deteriorated, and a plasticizer may be added to the mixed composition in consideration of production workability to adjust the glass transition temperature appropriately. It is preferable to select from the range of about 120 ° C. The stretching method may be a commonly used tube stretcher, and the stretched tube thus obtained can be wound into a product.

The thickness of the tube obtained as described above is not particularly limited, but as a shrink tube for a dry battery, it is usually 30 to 150 μm, preferably 50 to 10 μm.
0 μm.

In order to use the tube of the present invention as a shrink tube for a dry battery, the shrinkage rate in 30 seconds of hot water at 100 ° C. is 40% or less in the longitudinal direction, preferably 30% or less, and 40% in the radial direction. % Or more, preferably 45% or more. When the shrinkage ratio in the radial direction is not at least 40% or more, when used for a dry battery, the end portions are not in close contact with each other and are in a raised state, which is not suitable.

Even if the radial shrinkage is 40% or more,
If the shrinkage ratio in the length direction exceeds 40%, the coating position will shift when coated with an automatic coating machine for dry batteries, and further, the length of the cut must be increased, which is costly. Connected, unfavorable. The shrinkage ratio is determined by adjusting the stretching ratio and the stretching temperature according to the characteristics of the composition (mainly the glass transition temperature).

In the above-mentioned tube raw material resin composition, various additives usually used, for example, an ultraviolet absorber,
Antioxidants, stabilizers, colorants, fillers and the like can be added depending on the purpose.

[0018]

EXAMPLES Examples will be described below, but the present invention is not limited thereto. The following various characteristics were measured and evaluated as follows. (1) Shrinkage (%) After immersing in hot water of 100 ° C. for 30 seconds, calculation was performed in the length direction, the radial direction, and both directions. Shrinkage (%) = [(L ₀ −L ₁ ) / L ₀ ] × 100 L ₀ : Dimension before shrinkage L ₁ : Dimension after shrinkage (2) Dynamic friction coefficient According to JIS K-7125, lower test piece 25 mm ×
125 mm, the upper test piece is 15 mm x 120 mm,
The sliding piece has a holding area of 15 mm × 40 mm 5
It was measured by pulling the upper test piece as 0 g.

(3) Surface Roughness In accordance with JIS B-0601, the surface condition was measured using a roughness analyzer AY-22 manufactured by Kosaka Laboratory Ltd., and a 10-point average roughness was obtained. (4) Finishability Using an automatic machine (SW-1) for dry batteries manufactured by Nippon Automatic Seiki Co., Ltd., when a tube with a folding diameter of 23 mm and a cut length of 53 mm was coated on AA batteries and then heat-shrinked, the ends were The parts are not in close contact with each other and are in a standing state, or the coating position is shifted and coated.
The case where none of these inconveniences occurred was marked with “◯”.

(5) Opening property An opening device (SW-1) manufactured by Nippon Automatic Seiki Co., Ltd. is used to judge the opening property. The case where 5 defective openings were caused was designated as Δ, and the case where 6 or more defective openings among 10 were caused was designated as x. (6) Tensile elastic modulus (kgf / cm ² ) A test piece having a cut length of 360 mm and a width of 5 mm was used with a space between marked lines of 30 mm.
After setting to 0mm, the pulling speed is 100mm /
A tensile test was performed for each minute, and the load-elongation curve was used for calculation.

(7) Drop impact cracking After covering a tube with a folding diameter of 23 mm and a cut length of 53 mm on an AA dry cell, it was dropped from a height of 500 mm onto a concrete surface so as to drop from the edge of the dry cell.
The ones that did not crack the tube ○ 1 out of 10
The case where 5 cracks occurred was rated as Δ, and the case where 6 or more cracks occurred among 10 was marked as x. (8) Automatic machine running performance An automatic machine for dry batteries (SW-1) manufactured by Nippon Automatic Seiki Co., Ltd. is used to judge the running performance of the automatic machine, and there is no running trouble such as catching of the tube during running. ○ 1 out of 10
Five running troubles were evaluated as Δ, and 6 out of 10 running problems were evaluated as x. (9) Tensile Strength (kgf / cm ² ) The tensile strength was measured according to JIS C-213.

Experimental Example 1 Polybutadiene particles having an average particle diameter of 2 to 3 μm and a polybutadiene particle content of 3% by weight.
HIPS extruded by tubing, with an outer diameter of 8.0 mm,
An unstretched tube having a thickness of 0.20 mm was obtained. This was stretched 1.2 times in the length direction and 2.5 times in the radial direction at a stretching temperature of 120 ° C. to obtain a stretch tube. In the same manner, the polybutadiene contents shown in Table 1 were used for comparison, and various properties were evaluated.

[0023]

[Table 1]

As shown in Table 1, the weight ratio of the rubber particles is 3
~ 15 wt% No. Nos. 2 and 3 have a dynamic friction coefficient of 0.4 or less and a tensile elastic modulus of 150 kgf / mm ² or more, which is excellent in openability and running performance of an automatic machine. No drop impact cracks. On the other hand, the weight ratio of the rubber particles is 3% by weight.
No. less than In No. 1, the dynamic friction coefficient exceeds 0.4, so there is some concern about the opening property, and the drop impact cracking property is also inferior.
Moreover, No. 4 has a tensile modulus of 1
Since it does not satisfy 50 kgf / mm ² or more, the running performance of the automatic machine is poor.

(Experimental Example 2) HIPS having different average particle diameters of polybutadiene particles having a polybutadiene content of 3% by weight and 15% by weight was obtained in the same manner as in Experimental Example 1 to obtain a stretched tube. Compared with.

[0026]

[Table 2]

As shown in Table 2, No. The tubes of Nos. 5 to 12 all have good characteristics, but the No. 5 has a dynamic friction coefficient of more than 0.4. 5 has some anxiety about openness,
In addition, the tensile strength of No. ³ near 300 kgf / cm ²
Nos. 8 and 12 are a little worried about elongation and breakage due to tension in automatic machines. Comprehensively, No. 6-7, and No. 10-11 were especially excellent.

Experimental Example 3 Polybutadiene particles having an average particle diameter of 2 to 3.5 μm and a polybutadiene particle content of about 1
95 wt% of 0 wt% HIPS (Styron 475S manufactured by Asahi Kasei Corporation) and diisononyl adipate (DI
A stretched tube was obtained in the same manner as in Experimental Example 1 from a mixture of 4% by weight of NA) and 1.0% by weight of an inorganic lubricant (magnesium silicate) or an organic lubricant (erucic acid amide). Also, as shown in Table 3 in the same manner,
Compared.

[0029]

[Table 3]

As shown in Table 3, the shrinkage is 40 in the longitudinal direction.
% Or less, 40% or more in the radial direction, and a dynamic friction coefficient of 0.4
No. which satisfies the following: 13, and No. 15 to 17 are excellent in finishability and openability. On the other hand, 100% by weight of GP polystyrene containing no rubber particles was used. 1
In No. 4, the dynamic friction coefficient exceeds 0.4, and the opening property is poor. In addition, No. No. having a radial shrinkage of less than 40%. 1
No. 8, the shrinkage in the length direction exceeds 40%. 19
Both had poor finish and were unsuitable as a tube for coating dry batteries.

[0031]

EFFECTS OF THE INVENTION In the polystyrene heat shrinkable tube of the present invention, by simply specifying the amount of general-purpose HIPS conjugated diene hydrocarbon particles, a good elasticity (rigidity) for inserting a dry battery in an automatic dry battery coating device, It has strength and slipperiness on the inner surface.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area B29K 25:00 105: 02 B29L 23:00

Claims (4)

[Claims] 1. The conjugated diene hydrocarbon polymer particles are 3 to.
A heat-shrinkable polystyrene tube formed by stretching a tube made of high-impact polystyrene dispersed in 15% by weight. 2. The tensile strength in the longitudinal direction is 300 kgf /
The heat-shrinkable polystyrene-based tube according to claim 1, wherein the heat-shrinkable polystyrene-based tube is at least ² cm ² . 3. The tensile elastic modulus in the longitudinal direction is 150 kgf.
/ Mm ² or more, the heat-shrinkable polystyrene tube according to claim 1. 4. The contraction rate when immersed in hot water at 100 ° C. for 30 seconds is 40% or less in the length direction, 40% or more in the radial direction, and the dynamic friction coefficient of the inner surface is 0.4 or less. The heat-shrinkable polystyrene-based tube according to claim 1, wherein